1. Field of the Invention
This invention relates to thermoplastic polyamide compositions, more particularly, to thermoplastic compositions comprising a polyamide and a block polymer containing polyamide segments and other polymeric segments.
2. Description of the Prior Art
Polyamides are commonly employed as engineering thermoplastics. The balance of properties comprising strength, stiffness, impact resistance and dimensional stability makes polyamides especially attractive as replacements for metals in various structural applications, particularly in automotive applications because of the reduction in weight that can often be achieved.
Although unmodified thermoplastic polyamides have many uses as an engineering thermoplastic, considerable efforts in the prior art have been made toward achieving improved properties for polyamide engineering thermoplastics. Such efforts are typically directed at improving a particular property or at improving the combination of properties of the polyamide resin to make it more suitable for a particular application.
U.S. Pat. No. 4,174,358 issued Nov. 13, 1979 to B. N. Epstein is directed to thermoplastic polyamide compositions having improved ductility or toughness. The toughened thermoplastic compositions taught in Epstein contains 60 to 99% by weight of a polyamide matrix resin and 1 to 40% by weight of at least one other phase which contains another polymer dispersed as small particles within the polyamide matrix and having sites which adhere to the polyamide. The polymer modifier in the compositions taught by Epstein can be any of a wide variety of polymers provided that it meet certain requirements, e.g. that it have certain sites which adhere to the polyamide and that it meet a tensile modulus limitation of 1 to 20,000 psi.
Various other prior art concerned with improving the impact of polyamides is discussed in Columns 1 and 2 of the Epstein patent.
In U.S. Pat. No. 4,218,549 issued Aug. 19, 1980 to H. Jadamus et al. there are described compositions comprising a first component which is at least one polyamide and a second component described as at least ore polyether ester amide. These compositions are said to exhibit improved flexibility and cold impact strength. The polyamide component is from omega-amino-carboxylic acids or lactams having at least 10 carbon atoms. The polyether ester amide component is prepared by hydrolytic polycondensation employing the aforementioned carboxylic acids or lactams, an alpha, omega-dihydroxy(polytetrahydrofuran) and a dicarboxylic acid.
In U.S. Pat. No. 3,549,724 issued to K. Okazaki et al. on Dec. 22, 1970 there are described polymer blends comprising a polyamide and a polyether-polyamide block copolymer. The block copolymer is prepared by the polycondensation reaction of a polyamide producing monomer selected from lactams, omega-amino acids and diamines combined with dicarboxylic acids, in the presence of a polyether having terminal groups selected from amino groups, organic acid salts of such amino groups, carboxyl groups, organic amine salts of such carboxyl groups and mixtures thereof. The compositions are said to have high and durable antistatic properties. The same K. Okazaki and others disclose an improvement in the teachings of U.S. Pat. No. 3,549,724 patent to obtain compositions which are said to have even better antistatic properties in U.S. Pat. No. 3,639,502 issued Feb. 1, 1972. Polyamide-based compositions taught therein similarly are blends of a polyamide and a polyether-polyamide block copolymer.
In U.S. Pat. No. 3,636,135 issued Jan. 18, 1972 to J. D. Garforth et al. compositions said to be resistant to static electrification are disclosed which comprise an admixture of a synthetic linear polyamide and a polyetheresteramide which is a condensation product of an aliphatic dicarboxylic acid, a hydroxypolyoxyalkylene compound and certain amino acids, lactams, diamines or combinations thereof.
The present invention relates to novel compositions comprising a blend of a polyamide resin and a particular block polymer having polyamide segments, other polymeric segments and acyl lactam groups or imide residues thereof. This invention provides useful engineering thermoplastic compositions. Improved properties over the polyamide resin alone, e.g., improved resistance to break upon impact as measured by the notched Izod test ASTM D-256-56, are obtainable with the compositions of the present invention.